[sudo-workers] tty tickets

[Todd C. Miller]

That's an interesting idea.  Anything that changes the mode on the
tty, such as mesg(1) will cause the ctime to be updated but that's
not a common thing to do.

I think you can avoid having to store the tty's ctime directly in
the timestamp file by just comparing the tty's ctime to the mtime
of the timestamp file minus the value of timestamp_timeout.

 - todd